The program consists of four projects directed toward definition of requisites to language and the processes of language acquisition. The animal model project's general goal is to investigate the potential of the common chimpanzee (Pan troglodytes) and the pygmy chimpanzee (Pan paniscus) to learn and to use referential skills and communicative concepts in a variety of functional contexts and in so doing gain a better understanding of language, its functioning, its development, and its cognitive basis. A second project incorporates the principles derived from the animal model project into research designs to determine whether they are uniquely effective in fostering language acquisition in persons who by virtue of servere and profound retardation have not learned language to any significant degree. A third project places emphasis upon the computer-based system which we have developed across the years as a means of facilitating the maintenance of established language functions, testing their ranges of effective application/generalization, and teaching new functions. A fourth project addresses questions of brain function and laterality of function in particular. Whether the language skills manifested by our subjects reflect laterality and whether that laterality of function (if extant) is there initially or developed through the course of language learning will be studied.